Telephone-exchange system



A. E. LUNDELL AND F. A. STEARN.

E TELEPHONE EXCHANGE SYSTEM.

A. E. LUNDLLAND F. A..STEARN,

TELEPHONE EXCHANGE SYSTEM.

VAPPLICATION lFILED OCT. 8| 1917.V

Patented r Feb. 10,1920.-

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A. E. LUNDELL AND F. A. STEARN. TELEPHONE EXCHANGE sYsEM.

APPLICATION FILED OCT. 8, 19|?- Patented Feb. 10, 1920.

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ALBEN E. LUNDELL, 0F NEW YORK, NWY., AND FRANKLIN A. STEARN, OFPATERSON, NEW JERSEY, A'SSIGNORS TO WESTERN ELECTRIC COMPANY,INCORPORATED, 0F NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

TELEPHONE-excitait@ sYsTin/r.V

Specification of Letters Patent. Patented Feb. 10, 1920.

Application filed October S, 1917. Serial No. 195,356.

which the following is a full, clear, concise,

and exact description. l

This invention relates to telephone -exchange systems, and moreparticularly to improvements in systemsA vemploying machine switching.

The ob `ect of this invention is to provide the hunt for an-idle meansfor continuing trunk if all the trun is of a group normally associatedwith a selector switch are busy at the time that the hunting operationtakes place.

According to a feature of this invention the hunting selector switchafter having passed over all the trunks leading directly to selectorswitches for thc further extension of a line, passes to an idle overowtrunk.

Associated with each of l these overflow' trunks there isa rotatableswitch which is capable of hunting over an equivalent group of trunkscontinuously until an `idle trunk is found.

In the drawings, Figure 1 represents a calling subscribers line, anoperators connecting circuit and a selectorswitch; Fig. 2

(to be placed to the right of Fig. l) a sequence switch arranged toseize an idle connector switch to extend a call to a called subscribersline; and Fig. 3 (to be placed below Fig. 1) anoperators controllingapparatus by means of which the selector and connector switches may beset. ,4 Y l The selector and sequence switches and the controllingapparatus therefor will notk be disclosed in full in the followingdescription of this system, switches of this type being wellknown intheart. A complete description of such switches may be had from 'a PatentNo. 1,168,319, patentedmJanuary 8, 1916,to A. E A'Lundell. A

A The calling subscriber at station 100, desiring to obtain a connectionwith a suby `sc'riber at station l200, removes his receiver from theswitchhook, closing thus a circuit for line relay LR, which lights acalling signal lamp CL. `The operator, noticing lamp GL lighted, insertsa pluglOl into a jack 102 in which the calling line terminates,whereupon a circuit is closed from grounded` batterythrough the windingof cut-oli relay CR, the sleeve contacts of jack 102 and plug 101, andthe winding of a relay 103 to ground. Relay 103 closes a circuit 'fromground through its armature and front contact, a contactr104 andthepower magnet of a sequence switch 105 to grounded battery. Underthecontrol of anormal spring 106,

sequence switch 105 is movedout ofposim tion 1 into position 2'.' Acircuit is now closed from ground through sequence switch 'contact 107,conductor 108, a contact 300 of a sequence switch 301, and the windingof arelay 302 to grounded battery. Relay'302 becomes energized andcloses a circuit from ground through its left-hand armature and front.contact, a contact 303 and the power lmagnet of the sequence switch 301to grounded battery. Under the Control of a normal spring 304, sequenceswitch 301 is moved out of position 1 into position 3. Relay 302 doesnot become'de'nergized when sequence switch 301 leaves position 1,acircuit being yclosed from grounded battery through the winding of thisrelay, sequence switch contact 305, the right-hand armature and lirontcontact of relay 302, conductor 306 and contact 109 of sequence switch105, to ground.

v The operator by depressing her listening key 110, connects hertelephone set 111into telephonie yassociation with the callingsubscriber, and, in accordance with instructions received from vthesubscriber, she adjusts her controlling apparatus. Only two rows of keysare shown in Fig. 3, as it is thought suiiicient forA the purpose of thepresent invention. lIt will be obvious to those skilled in the art thatthe` switches used will be set in accordance with ra plurality of digitsin order to extend the calling line toward the called line and that forthis purpose a plurality of rows of keys must be yprovided at theoperators position. Supposing, however, that thel called subscribersline may be seized by causing selector switch 130 to take three steps,the operator will depress key 310 and similar keys for controllingconnector switches and a start-key 312. A circuit is established fromground through the contact of key 312, a

- contact 313, and the power magnet of se- `quence switch 301 togrounded battery, Jfor moving this sequence switch into position 4.

A circuit is then closed from grounded battery through the windingofrelay 113, sequence switch contact 114, conductor 115, the outerarmature and back contact of the upper counting relay O, the winding ofa stepping relay 315, sequence switch contact 314, conductor 316, and asequence switch contact 116 to ground. Relays 113 and 3 15 becomeenergized. Relay 113 closes a circuit from ground through its,right-hand armature and front contact, a sequence switch contact 117,conductor 118, and the power magnet f the sequence switch 105 togrounded battery, for moving this sequence switchinto position 3. Relay113 remains energized upon the opening of contact 114, due to theclosure o'l' a substitute path through the left-hand armature and frontcontact of this relay, and a sequence switch contact 119.

Upon the energization of relay 315, a circuit is closed from groundthrough the front Contact and armature of this relay, asequence switchcontact 317 conductor 318, the con` i tact of the key 310, conductor322, the armature and back contact of the upper counting relay 2 and thewinding of the lowel1 counting relay 2 to grounded battery. The lowercounting relay 2 closes a circuit Jfrom ground through sequence switchcontactv 320, conductor 321, the armature and front Contact of the lowercounting relay 2, andthe windings of the upper and lower counting relays2 to grounded battery. The upper counting relay 2, however, can notbecome energized due tothe closure of a short circuit around c itswinding from ground through sequence switch contact 317, to groundthrough the Y armature and front contact of stepping re- 128 is moved inan upward direction, the

wipers 124, 125, 126 wiping over a terminal bank 129 and the commutatorbrushes 127,

128 over conducting and insulated segments f of a commutator plate112..v Vhen the com- Amutator brush 128 engages a conducting segment131, it connects ground `through this segment, a conductor 132, sequenceswitch contact 133 and 119 to relay 113,thus shunting out relay 315.Relay 315 opens at v. renergization of relay 315, which again ,con-

vthrough sequence yswitch contact 324, the

its front contact the short circuit of the upper counting relay 2,whereupon.V this counting relay becomes energized and connects conductor322, through its armature and front contact, the armature and backcontact of the upper counting relay 1, the winding pf the lower countingrelay 1, and conductor 323, to grounded battery. The lower countingrelay 1 connects now the upper counting relay 1 .into circuit. Thisrelay, however, can not become energized due to the fact that commutatorbrush 128 moved `in the meantime into engagement with an insulatedsegment 134, permitting thus the nects ground to conductory 322.

The operation of the counting relays continues in substantially the samemanner until the selector 130 has-been moved upward by three steps andthe upper counting k.relay O has become energized. This counting relayopens, at its outer armature, the fundamental circuit including relays315 and` 113, and closes a circuit from ground vinner armature and frontcontact of .the upper counting relay O and the power magnet of sequenceswitch 301 to grounded battery, yfor moving .this sequence switch intoposition 6. When the sequence switch leaves f `position 4, allthecounting relays which have been locked up become denergized.

Relay 113, upon denergization, opens the circuitof magnet 120. andcloses a circuit from ground, through its right-hand armature and backcontact, sequence switch contact 135, conductor 118, and the powermagnet of sequence switch to grounded battery, for moving this sequenceswitchout ofposition 3 and into position 6.

circuit is now closed from. ground through sequence switch contacts 136and 137, and the left-hand winding of a relay 138, to grounded battery.

The energization of relay v138 closes a cir- 110 cuit from ground, outerright-hand armature and front contact of this relay, sequence switchcontact 140,*conductor 1.18 andthe power magnet of sequence switch 105to Vgrounded battery, whereupon the sequence n.5

switch will be moved into position 7. Vhen the sequence switch 105leaves position 6, the circuit above traced for relay 138 is opened atcontact 136, butthis relay remains energized due tothe closureof acircuit from grounded battery, right-hand winding of relay 138, innerright-hand armaturel and ront contact vof this relay, conductor 152,

brush 126, to ground over the test conductor of the trunk with whichbrush 1.26is in engagement, provided this trunkis busy. 1n position 7 acircuit is completed for updrive magnet 120, ifrelay 138 is energized,from ground, battery, winding of the magnet, contact 145, outer armatureand front contact of relay 138 to ground, thus causing the movement ofthe selector onto the terminals of another trunk.

Let us suppose that all the trunk lines extending direct to finalselector switches in the third group of contacts of the bank 129 arebusy, that is to say, ground is to be lay 138 becomes denergized andopens the circuit of magnet 120, thus arresting the brush rod 123. Relay138 closes a circuit from ground through its outer right-hand armatureand back contact, sequence switch contact 146, conductor 118 and thepower magnet of sequence switch 105 to grounded battery for driving thissequence switch into position l1.

In position 11 of sequence switch 105, a vcircuit is completed fromground, contact 116, conductor 316, contact 151, brush 125, conductor'203, lower armature and back contact of relay 205, left-hand armatureand back contact of relay 206, left-hand winding of relay 207 togrounded battery. Relay 207 completes circuit from grounded battery,winding of relay 208, right-hand armature and back contact of relay 206,left-hand armature and front contact of relay 207 to ground. Relay 208completes a locking circuit for itself fromgrounded battery, winding ofrelay 208, inner left hand armature and front contact of this relay,"conductor 209, terminal 139, brush 126, conductor 152, inner right-handarmatureL and back contact of relay 138, contact 153 to ground. Relay208 closes a circuit from grounded battery, winding of relay 206, outerleft-hand armature and front contact of relay 208, lower armature andYback contact of relay 205 to ground over conductor 203.

The sequence switch 225 does not have a definite normal position, butremains in engagement with the last trunk to which 1t extended a call.When this trunk becomes idle and is later seized by a selector switchsimilar to 130, ground will be placed upon the test wire 211 throughcontact similar to 153 at this selector switch. Therefore when relays208 and 207 become energized in the manner above described a lockingcircuit for relay 207 is completed from grounded battery right-handwinding and right armature and front contact of this relay, outerright-hand armature and front contact of relay 208, contact 1, 2, 3, 4,5, 6, 7 or 8 of sequence switch 225, test conductor 211 to ground. Thislocking circuit prevents the denergizat-ion of relay 207 when vrelay 206becomes energized in the manner above described. Relay 206 thereforecompletes a circuit from grounded battery, winding of power magnet ofsequence switch 225, right-hand armature and front contact of relay 206,left-hand armature and front contact of relay 207 to ground.

This circuit causes the sequence switch to move into its next positionwherein the above operation will again be performed, provided the trunkthere encountered is busy. While the sequence switch is moving from oneposition to the next, a circuit is completed through the left-handwinding of relay 207 in order to maintain this relay energized. This maybe traced from grounded battery left-hand winding of relay 207,left-hand armature and front contact of relay 206, contact 214, lefthand armature and front Contact of relay 207 to ground.

We will assume that when the sequence switch 225 reaches the seventhposition, it finds an idle trunk. The circuit through the right-handwinding of relay 207 will then be opened, since no ground will be foundupon the test conductor 211. Relay 207 therefore denergizes and opensthe circuit for the motor magnet of the sequence switch. Relay 207 alsocloses a circuit from lgrounded battery, winding of relay 205, innerright-hand armature and front contact of relay 208, left-hand armatureand back contact of relay 207 to ground.

Relay 205 opens the circuit of relay 206 and extends the conductors 202and? 203 through to the connector switch wassociated with the selectedidle trunk. Relay 205 also by attracting its upper armature corn--pletes the fundamental circuit through to the stepping relay (notshown) at the con nector switch. This stepping relay will be controlledin the well known manner to operate the connector to complete theconnection to the called subscriber substation 200. Since this operationdoes not form part of this invention, it is believed that a completedescription of the operation is unnecessary. y y

The subscribers desiring disconnection restore their receivers to theswitchhoolrs, causing thus, in the well-known manner, the actuation ofsupervisory signals 160 and 161. The operator noticing the actuation ofthese sign als removes plug from jack 102, whereupon relays CR and 103become denergized, the -latter closing a circuit from ground through itsarmature and back contact, and a contact 162 and the power magnet ofsequence switch 105 to grounded battery, whereupon this sequence switchis moved into position 18. In position 18 of the sequence switch, acircuit is closed from grounded battery, through the winding of magnet168 and a sequence switch contact L 164 toy ground. Magnet 163 presses,by means of its armature 165, the brush rod 123 against a roller 166constantly rotating in the direction indicated by the arrow, andthebrush ro d with the wipers and brushes mounted thereon is lowered. lVhenthe brush rod reaches its normal position, a circuit is closed fromground, through commutator brush 128, a conducting segment 167,conductor 168, a contact 169conductor 118, and the power magnet ofsequence switch 105 to grounded battery, yfor moving this sequenceswitch out of posit-ion 18 into position 1. Vhen the sequence switchleaves position 18, magnet 163 becomes denergized.

As soon as sequence switch 105 leaves position 16, the contact 153 isopened, causing the denergization of relay 208, which in turn opensthecircuit of relay 205.

Relay 208 removes ground from test conductor Q11, thus causing thereleasevof the connector switch in the well known manner.

If the sequence switch 225 had been in position 7 at the time theoverflow trunk was seized by the selector 130 no ground would have beenfoundupon the test wire 211 for completing the locking circuit of relay:207 through its right-hand winding and armature and therefore when therelay 206 is energized in the manner above described the relay 207denergizes, since contact 214 is yopen in position 7. Relay 207 is soconstructed that it will release its armatures before the circuit of thepower magnet of sequence switch 225 is completed through the frontcontact of relay 206. vThe sequence switch will therefore remain inposition 7 lhat is claimed is:

1. In an automatic telephone system, incoming lines, groups of trunks,overflow trunks associated with each group of trunks, a hunting switchassociated with each overflow trunk, a group of trunks terminating ateach of said switches, said switches being arranged to be normally inengagement with any one of the .said last mentioned trunks terminatingthereat, means for connecting an incoming line to an overflow trunk,means actuated'by said connection for operating the switch associatedwith said overflow trunk to extend the connection to the trunk withwhich it is in engagement if said trunk is idle or to start hunting foran idle trunk if said trunk is busy, and means for stopping .said switchupon the` first. idle trunk eneased- 2. In an automatic telephonesystem, incoming lines, groups of trunks, overflow trunks associatedwith each groupv of trunks, a hunting switch associated with each`overflow trunk, said switches having no definite normal positions, agroup of trunks terminating at each of said switches, means forconnecting an incoming line to an overflow trunk, means actuated by saidconnection for operating the switch associated with said overow trunk toextend thev incoming line to an idle trunk.

3. In an automatic telephone system, incoming lines, groups of trunks,overflow trunks associated with each group kof' trunks, a hunting switchassociated with each overflow trunk, a group of trunks terminating ateach of said switches, each of said switches having no definite normalpositions and being arranged to be normally in engagement with any oneof the trunks terminating thereat, means for connecting an incoming lineto an overflow trunk, means actuated by said connection for operatingthe switch associated with said overliow trunk to extend the connectionto the trunk with which it is in engagement if said trunk is idle or tostart hunting for an idle trunk if said trunk is busy, and means forstopping said switches upon the first idle trunk engaged.

Ll. In a telephone system, a line, a selective switchv for extendingsaid line, groups of trunks terminating in said switch, overflow trunksassociated with each said group, means for selectively setting saidswitch in association with any of said groups, means responsive to thebusy condition of all trunks constituting said selected group forsetting said switch on an idle -oneof said overflow trunks, anequivalent group of trunks associated with each overflow trunk, aunidirectional rotatable selective switch having no normal position forautomatically ALBEN E. LUNDELLj FRANKLIN A. STEARN.

